//介绍#define语句
#include <stdio.h>

#define YES 1
#define NO 0

//判断number是否为偶数
int isEven(int number){
  if (number%2==0) {
    return YES;
  }
  return NO;
}

int main(int argc, char const *argv[]) {
  int isEven(int);
  int numbers[] = {17,18,19,20};
  for (int i = 0; i < 4; i++) {
    int number = numbers[i];
    if (isEven(number) == YES) {
      printf("%i is even.\n",number);
    }else{
      printf("%i is not even.\n",number);
    }
  }
  return 0;
}
